Desizing, scouring and bleaching cotton/polyester fabrics containing portions dyed with sensitive dyestuffs

ABSTRACT

A method of desizing, scouring and bleaching greige cotton/polyester fabrics containing colored portions constructed of yarns dyed with an excess of sensitive dyestuffs without incurring color markoff upon, or bleeding into the white background portions of the fabric. The dry greige fabric is first singed then quenched with steam or a water mist under conditions preventing a water pickup exceeding 30 percent of the fabric weight. The fabric is then passed through a multidip-type rope washer used as a treating chamber in which the solution contained therein is a hot alkaline solution of surface active agent held at 160*-210* F. and is at a solution to fabric weight ratio of 20-40:1. The motion of the fabric through the solution and alternate dipping and squeezing action of the solution through the fabric acts to scour, desize and remove excess dyestuff therefrom. After then washing thoroughly with water, the fabric is finally saturated with a peroxymonosulfate solution buffered at a pH of 5 to 8.5, then heated in the saturated condition at a temperature of 100*-212* F. to effect bleaching.

AU 165 EX United States Patent [72] inventor n Appl. No.

[22] Filed [45 Patented [73 l Assignee Marvin H. Rowe Wilmington. Del.

Feb. [7. 1970 Nov. 9. [971 E. I. du Pont de Nemours and Company Wilmington. Del.

[54] DESIZING, SCOURING AND BLEACHING COTTON/POLYESTER FABRICS CONTAINING PORTIONS DYED WITH SENSITIVE DYESTUFFS Primary Examiner-Mayer Weinblatt Attorney-Edwin B. Broding ABSTRACT: A method of desizing, scouring and bleaching greige cotton/polyester fabrics containing colored portions constructed of yarns dyed with an excess of sensitive dyestuffs without incurring color markoff upon. or bleeding into the white background portions of the fabric. The dry greigc fabric is first singed then quenched with steam or a water mist under conditions preventing a water pickup exceeding 30 percent of the fabric weight. The fabric is then passed through a multidip-type rope washer used as a treating chamber in which the solution contained therein is a hot alkaline solution of surface active agent held at l60-2 l0 F and is at a solution to fabric weight ratio of 20-40:]. The motion of the fabric through the solution and alternate dipping and squeezing action of the solution through the fabric acts to scour. desize and remove excess dyestuff therefrom. After then washing thoroughly with water. the fabric is finally saturated with a peroxymonosulfate solution buffered at a pH of 5 to 8.5. then heated in the saturated condition at a temperature of l()02l2 F to effect bleaching.

DESIZING, SCOURING AND BLEACHING COTTON/POLYESTER FABRICS CONTAINING PORTIONS DYED WITH SENSITIVE DYESTUFFS CROSS-REFERENCE TO RELATED CASE Pending Stalter application Serial No. 691,970, filed Dec. 20, 1967 now U.S. Pat. No. 3,556,710.

BACKGROUND OF THE INVENTION The bleaching of textile fabrics containing portions dyed with sensitive dyestuffs, such as the naphthol disperse, vat and fiber reactive dyes, has long been a problem. For example, when cellulosic fabrics containing portions dyed with naphthol dyes are bleached, there is a marked tendency for the dyes to bleed and markoff onto the undyed portions of the fabric, or onto other goods they may come into contact with during bleaching. Since the tendency of such dyed portions to stain or markoff is aggravated by severe bleaching conditions, particularly high temperatures, high alkalinities and extended bleaching times, mild bleaching conditions have generally been considered essential.

Patents proposing bleaching methods employing hydrogen peroxide under mild conditions such as temperatures no higher than about 160 F. and pH conditions of about 6.5 to are Kaufimann U.S. Pat. No. 2,391,700 and Smollens U.S. Pat. Nos. 3,280,039 and 3,343,906. Prett et a1. U.S. Pat. No. 3,227,655 proposes bleaching with peracetic acid solutions at a pH of 4.6 to 6 and a temperature of 60' to 90 A more recent proposal is described in the pending application of Slaltcr, Scr. No. 691,970, filed Dec. 20, 1967 now U.S. Pat. No. 3,556.10, wherein the fabric containing portions dyed with a sensitive dyestuff is bleached by the use of a solution of a peroxymonosulfate buffered at a pH of 5 to 8.5. While the above prior methods possess merits, they are not entirely satisfactory, particularly when the greige fabric to be bleached contains dyed yarns having thereon excess or loosely held sensitive dyestuff, as is often the case. This is because such excess or loosely held dyestuffs sluff-off or markofi' very readily onto the undyed portions of the fabric when the greige fabric is sub jected to the usual water or solution quenching following the singeing, and subsequent desizing and/or scouring preparatory treatments which usually involve one or more treatments while the fabric is piled or stacked in the damp state. Thus, the usual desizing and/or scouring treatment involves saturating the fabric with a desizing and/or scouring solution, and allowing the saturated fabric to stand, often at an elevated temperature, for a suitable period of time. Dyestuff marked off onto the undyed portions during such saturation preparatory treatments is generally not removed during subsequent bleaching with a peroxygen compound, in view of which an after treatment with a hypochlorite solution is often used. However, fabrics constructed of blends of cotton and polyester fibers do not respond to such hypochlorite after treatment because markedoff colors become fixed to the polyester fibers of the blend and hypochlorite solutions strong enough to remove stains from the cotton portion destroy some of the color on the dyed yarn resulting in a loss of color value.

Thus, there is a need in the textile industry for a simple but effective method, preferably one that can be practiced continuously, for processing greige cotton/polyester fabrics having colored portions constructed of yarns dyed with an excess of sensitive dyestuffs through preparatory and bleaching steps without incurring color markoff upon, or bleeding into, the white background of the fabric. The present invention is directed to a method satisfying such a need.

SUMMARY OF THE lNVENTION The method of the invention is a method for continuously processing greige cotton/polyester fabrics having dyed portions constructed of yarns dyed with an excess of a sensitive dyestuff loosely held thereon through preparatory steps and a bleaching step without incurring color markoff upon, or

method involves continuously: (l) singeing the dye greige fabric with a flame; (2) quenching or extinguishing flame on the fabric by exposing the fabric to steam or to a water mist controlled to avoid a water pickup by the fabric greater than 30 percent of the fabric weight; (3) desizing and scouring the fabric and removing said loosely held dyestuff therefrom by treating in a conventional multidip rope washer with an alkaline water solution of a surface active agent at a temperature of 160 to 210 F. and at a solution; fabric weight ratio of 20 to 40:], then washing the fabric thoroughly with water; and, (4) saturating the fabric with a solution of a peroxymonosulfate buffered at a pH of to 212 F. to effect bleaching thereof DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS The fabrics to be treated in accordance with the invention are blends of cotton and polyester fibers in the greige state, i

which fabrics will include colored portions constructed of yarns dyed with sensitive dyestuffs and having thereon excess or loosely held sensitive dyestuffs, such as the naphthol, disperse, vat, and fiber reactive dyestuffs. Such fabrics are problem fabrics in that the excess or loosely held dyestuffs present on the fibers in the colored portions of the fabric readily markoff on, or bleed into, the white background portions of the fabric whenever the fabric in the damp condition, i.e., saturated with water or with a solution for treating the fabric preparatory to bleaching, is roped, piled or stacked so as to cause the colored portions to contact the white background portions while the fabric is in the damp condition. The method of the invention can be successfully applied to such fabric alone or together with other fabrics, e.g., fabrics containing similar colored portions which, however, are free of excess or loosely held sensitive dyestuffs.

In accordance with the invention, greige fabric of the above type is singed in conventional manner by exposing all surfaces of the dry fabric momentarily to a flame jet, following which any flame on the fabric is extinguished or quenched by subjecting all surfaces of the fabric to a jet of steam or a spray with a fine mist of water. When quenching by spraying with a water mist, the time of contact with the spray should be such that the water content of the fabric immediately after the spraying does not exceed 30 percent of the dry weight of the fabric, the preferred water contents being about 8 to 20 percent. If the water content of the fabric at this point exceeds 30 percent and the fabric becomes roped, piled or stacked before proceeding with the next treatment stage, color markoff onto undyed portions of the fabric will generally occur. By limiting the water content as indicated, color markoff is prevented. In contrast, when fabric is singed then quenched by the usual practice of immersing the fabric in water or a treating solution, highly objectionable markoff or bleeding of the excess or loosely held dyestuff generally occurs.

Afler singeing and quenching the greige fabric as indicated above, the fabric is then subjected to a treatment for removing the loosely held dyestuffs, which treatment also and simultaneously effects desizing and scouring of the fabric. This involves passing the fabric in rope form through a treating solution containing about 0.1 to 2 percent, preferably 0. 2 to l percent, by weight, of a water-soluble organic surface active agent and an amount of an alkaline material sufficient to adjust the alkalinity of the solution to a pH of 9 to 13, preferably 10 to 11. The treatment should be effected at a solution to fabric weight ratio of 20 to 40:1, preferably 25 to 30:1, using the solution in a conventional multidip (at least 10 dips, preferably 20 or more) rope washer. The solution should be maintained at a temperature of to 210 F., preferably to F., during the treatment. The surface active agent in the treating solution assures the rapid wetting and penetra= tion of the fabric by the solution and prevents the redeposition of the excess or loosely held dyestuffs that are removed from bleeding into, the white background portion of the fabric. The 75 the fabric during the treatment by keeping them suspended in the solution. The alkalinity of the solution assists in the removal of such excess or loosely held dyestuffs from the fabric and effects the removal from the fabric of the usual sizing materials as well as naturally occurring or added waxes and the like materials. The fabric immersion time in the treating solution at the temperatures indicated generally should be at least 15 seconds but should not exceed about 3 minutes. The preferred immersion times are from about 7.5 seconds to l ,5 minutes. Times less than than about 15 seconds usually are not adequate to effect satisfactory desizing, scouring and removal of the excess or loosely held dyestuffs. Times greater than about 3 minutes should generally be avoided since the tendency for the dye in solutions to redeposit on the white portions increases with the increase in the immersion time. A solution flow through the rope washer at a rate, on a weigh basis, of from about I to 2 parts of solution per one part of fabric (on a dry basis) being processed is generally satisfactory to prevent excess buildup of removed dyestuffs in the treating solution. The preferred rate is about L2 to 1.5 parts of solution per part offabric.

In preparing the solution for the above treatment, any ofthe common water-soluble organic anionic or nonionic surface active agents may be used. These include the common watersoluble alkali metal, ammonium or alkanolamine soaps of the higher fatty acids such as the fatty acids of tallow, lard, coconut oil, palm oil, soybean oil, castor oil, fish oils and the like, and the corresponding soaps of synthetically produced higher fatty acids such as those produced by the oxidation of petroleum and by the well-known Fischer-Tropsch process. Suitable synthetic anionic surface active agents include the water-soluble salts, e.g., the alkali metal, ammonium and alkylolamine salts of sulfates and sulfonates of organic compounds containing a long chain (.g., 8 to 20 carbons) alkyl radical, such as the salts of sulfates obtained by sulfating the higher alcohols resulting from the reduction of the glycerideof tallow or coconut oil, the salts of long chain (e.g.,9to l8 carbons alkylbenzene sulfonates or alkyl glyceryl ether sulfonates, and the salts of coconut fatty acid monoglyceride sulfates and sulfonates. Suitable synthetic nonionic surface active agents include the condensates of ethylene oxide with the long chain aliphatic alcohols such as coconut alcohol, or with an alkylphenol (one containing a 6 to 12 carbon alkyl group) such as nonylphenol, in which from about 10 to 30 moles of ethylene oxide is condensed per mole of the aliphatic alcohol or the alkyl phenol. Other suitable nonionic surface active agents are the trialkylamine oxides in which one of the alkyl groups contains from about 10 to 18 carbon atoms and to ether linkages and 0 to 2 hydroxy groups, while the other alkyl groups contain 1 to 3 carbon atoms, e.g., dodecyldimethyl or dodecyldiethyl amine oxide; also similar trialkyl phosphine oxides and long chain dialkyl sulfoxides.

Any of the common alkaline materials capable of imparting a pH of9 to l3,preferably 10 to l l, to the above treating solution may be used in preparing the solution. Examples of such alkaline materials are the alkali metal hydroxides, the alkali metal carbonates, the alkali metal orthophosphates and the alkali metal molecularly dehydrated phosphates. Specific examples of such materials are sodium and potassium hydroxides, sodium and potassium carbonates, trisodium and tripotassium orthophosphates sodium and potassium pyrophosphates, sodium hexametaphosphates and sodium tripolyphosphate. The solutions may include one or more of'such alkaline materials and those which include at least one of the phosphates such as trisodium orthophosphate are preferred. Whatever of such alkaline materials or mixtures of two or more thereof, that are used, they should be present in the solution in amounts sufficient to impart a solution pH of9 to 13, preferably 10 to ll.

Following the above treatment with alkaline solution of a surface active agent, the fabric should be washed thoroughly so as to remove all residues of the treating solution from the fabric. At this stage, all of the excess or loosely held dyestuffs will have been removed from the fiber surfaces and washed free of the fabric. Preferably, the treated fabric is subjected to a hot water wash, e.g., at about 140 to I F., and then to a cold water wash, e.g., at about 70 to 80 F., using, for example, in each instance a conventional multidip-type rope washer.

Bleaching of the fabric is effected by saturating the fabric with an amount of the bleaching solution equal to from about 50 to 150 percent, preferably 80 to 120 percent, of the dry weight of the fabric, and then heating the saturated fabric at a temperature of from to 2] 2 F., for a time of from about 10 minutes to 5 hours, the higher temperatures generally requiring shorter times than lower temperatures. A very practical way of carrying out the bleaching involves impregnating or saturating the fabric with the bleach solution at about room temperature, then heating the saturated fabric, e.g. by contacting it with live steam or a suitable mixture ofsteam and air, depending upon the temperature desired. Most preferably, a continuous length of the fabric is continuously saturated with the bleaching solution, e.g., by immersing the fabric in the bleach solution, then expressing excess solution from the fabric, following which the saturated fabric is continuously heated by contact with live steam or a suitable mixture of steam and air, then stored, e.g., in a J-box or other suitable storage facility, from which the fabric is continuously withdrawn after a residence time therein equal to the desired bleaching time. Bleaching of the fabric can be effected in open width or rope form in the widely used continuous bleach .l-box ranges with no significant modification ofthe equipment being required. The bleached fabric will finally be subjected to one or more washes with water to remove all residues ofthe bleach solution. I

The bleach solution employed in the above bleaching operation is an aqueous solution containing dissolved therein a peroxymonosulfate in an amount such as will provide a concentration of active oxygen of from 0.005 to 1 percent, preferably 0.03 to 0.2 percent. As disclosed in the pending Stalter application Ser. No. 69l,970,filed Dec. 20, 1967 now U.S. Pat. No. 3,556,710, the peroxymonosulfate bleach solution should be buffered to a pH within the range of 5 to 8.5, preferably 5.5 to 7.

Any of the water soluble peroxymonosulfates such as the alkali metal, ammonium or the alkaline earth metal peroxymonosulfates can be employed in preparing the bleach solution. The most preferred peroxymonosulfate is the potassium peroxymonosulfate triple salt compound of the formula KH- SO 'K SO,'2KHSO A product comprising such triple salt compound and containing about 4.7 percent active oxygen by weight is available commercially. The peroxymonosulfate component of the bleach solution can also be formed in situ in the bleach solution by the reaction of peroxymonosulfuric acid (also called Caros acid), H,S0 and an alkali such as caustic soda, caustic potash, ammonium hydroxide, or an alkaline salt such as sodium or potassium carbonate, or the like.

The peroxymonosulfate bleach solution should be buffered to a pH within the range of5 to 8.5, preferably 5.5 to about 7. If the pH is lower than about pHS, the solution may be sufficiently acidic to damage cotton fibers. On the other hand, if the pH is higher than about 8.5, the solution becomes less stable. When the solution is buffered during the entire bleaching period to a value within the range stated, excellent bleaching of the undyed portions, i.e., the white background portions, of the fabric occurs with little or no bleeding of dyes from the dyed portions resulting and, consequently, with little or no staining of, or color markofi' onto, the undyed portions.

The commercially available potassium peroxymonosulfate triple salt product is quite acidic, so that solutions thereof will generally require at least partial neutralization with an alkaline material in order to bring the pH of the solution within the range 5 to 8.5. Such adjustment of the solution pH can be effected by suitable additions of any of the common alkaline materials such as sodium, potassium or ammonium hydroxide, or various alkaline salts, but it is also desirable that a salt having buffering properties such as will maintain the pH within the above range during the entire bleaching period also be present. The alkali metal phosphates particularly tetraalkali metal pyrophosphates such as tetrasodium pyrophosphates and trisodium phosphates. are particularly effective for this purpose, although other buffering agents such as sodium bicarbonate, the combination of borax and phosphoric acid, or of tetrasodium pyrophosphate and sodium acetate may also be used.

The invention is illustrated by the following examples. In the examples and elsewhere herein, all proportions or ratios and all compositions or concentrations expressed as percentages are by weight. In the examples, the abbreviation PMS is used to designate the commercially available potassium peroxymonosulfate product comprising the triple salt KHSO -K, S0 2, and having an active oxygen content of about 4.7 percent.

EXAMPLE I A greige gingham fabric which was a 50:50 blend of cotton and polyester (ethylene glycol terephthalate) fibers containing naphthol red-dyed areas in check and stripe patterns containing an excess or loosely held dye in the fibers in the dyed areas was singed in conventional manner by passing the dry fabric in open width form between opposing flame jets. Flame on the fabric was immediately quenched by next passing the open width fabric between opposing jets of steam. The fabric was then roped through poteyes and passed in rope form at a rate of about 200 yards/minutes through a multidip 28 clips) rope washer to which was fed continuously a water solution containing 0.3 percent of a commercial sodium dodecylbenzene sulfonate and 0.5 percent trisodium onhophosphate and having a pH of l l. The rate of feed of the solution to the washer and the overflow of solution therefrom was at a rate of about 1.5 times the rate of feed of the fabric through the washer, on a weight basis. The fabric passed through the washer in serpentine fashion so as to make about 28 dips into and out of the solution. The solution in the washer was maintained at about 180 F. and the residence time of the fabric in the solution was about 28 seconds.

The fabric exiting from the above washer was fed through a second similar washer through which was similarly passed water maintained at about 150 F. It was then similarly washed in a third similar washer through which was similarly passed water at room temperature (76 F.).

The washed fabric was then saturated with an amount of a bleach solution (about equal to the dry weight of the fabric) by immersing it in the bleach solution at room temperature, then expressing excess solution from the fabric. The bleach solution contained 1.6 percent PMS, 0.25 percent trisodium phosphate, and l.l percent sodium acetate. It had a pH of 6.4. The saturated fabric was then bleached by passing it continuously through a J-box maintained at about 170 F. with a mixture of steam and air. The rate of travel of the fabric through the .l-box was such as to give a residence time therein of about 90 minutes. The bleached fabric withdrawn from the J-box was washed thoroughly with water at about 150 F. The resulting fabric was well bleached and showed no evidence of color bleeding or markoff onto the white background portions, even though the starting fabric contained excess loosely held dye on the fibers in the colored areas.

EXAMPLE 2 A greige fabric which was about a 50:50 blend of cotton and polyester (ethylene glycol terephthalate) fibers and contained blue stripes on a white background with the blue stripes consisting of cotton fibers dyed with a vat blue dye and polyester fibers dyed with a disperse blue dye, was singed as described in example 1 then all surfaces of the fabric were exposed to a fine mist of water to quench or extinguish surface flames. The time of exposure to the water mist was such that the water pickup was about l0 percent of the dry weight of the fabric. The fabric was roped through poteyes, then passed through a multidip rope washer as described in example l where it was treated at I F. with a solution containing 0.5 percent sodiand showed no evidence of color bleeding or markoff onto the white background portions, even though the colored stripes of the starting fabric contained excess loosely held dyes on the fibers.

EXAMPLE 3 A greige fabric which was about a 50:50 blend of cotton and polyester (ethylene glycol terephthalate) fibers and contained a red-checked pattern on a white background with the red checks consisting of red yarn containing cotton fibers dyed with a naphthol red dye and polyester fibers dyed with a disperse red dye, was singed, then quenched with a fine water mist as described in example 2 The quenched cloth, having a water content of 20 percent, was stored in rope form in a large bin, from which it was continuously withdrawn and continuously processed through the treating steps described in example 2. The resulting fabric was well bleached and showed no color bleeding or markoff onto the white background portions, even though the colored checks of the starting fabric contained excess loosely held dyes on the fibers.

I claim:

l. A method of desizing, scouring and bleaching fabrics which are blends of cotton and polyester fibers and which contain dyed portions constructed of yarns dyed with an excess of sensitive dyestuffs loosely held thereon, said method comprising continuously: (l) singeing the dry greige fabric with a flame; (2) quenching flame on the fabric by exposing the same to steam or to a water mist controlled so as to avoid a water pickup by the fabric greater than 30 percent of the fabric weight; (3) desizing and scouring the fabric and removing said loosely held dyestuff therefrom by treating the fabric in a multidip rope washer with a solution of an anionic or a nonionic organic surface active agent having a pH of 9 to 13 at a solution: fabric weight ratio of 20 to 40:1 and a temperature of l60 to 210 F., then washing the fabric; and (4) saturating the fabric with from about 50 to I50 percent of its weight of a solution of a peroxymonosulfate buffered at a pH of 5 to 8.5, and heating the saturated fabric at a temperature of to 212 F. to effect bleaching (5) and washed thoroughly with water.

2. The method of claim I, wherein the solution employed in step (3) is a 0.l to 2 percent solution of n anionic surface active agent and has a pH of IO to ll.

3. The method of claim 1 wherein the peroxymonosulfate solution employed in step (4) is buffered at a pH of 5.5 to 7.

4. The method of claim 2 wherein the peroxymonosulfate solution employed in step (4) is buffered at a pH of 5.5 to 7.

i i t i i gggg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5 6]9 1 11 Dated November 1 lQT'l Invent flsd Marvin H Rowe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, line 52, before U delete and Claim 2, line 59, before "anionic: delete "n" and substitute Signed 11nd sealed this Ltth day 1f July 1972.

(SEAL) Attest:

EDWARD ILFLEIC ER, JR.

R0 BERT GOTT SC HALK Attesting Officer Commissioner of Patents 

2. The method of claim 1, wherein the solution employed in step (3) is a 0.1 to 2 percent solution of n anionic surface active agent and has a pH of 10 to
 11. 3. The method of claim 1 wherein the peroxymonosulfate solution employed in step (4) is buffered at a pH of 5.5 to
 7. 4. The method of claim 2 wherein the peroxymonosulfate solution employed in step (4) is buffered at a pH of 5.5 to
 7. 